Embodiments of the present invention relate to a pipeline termination arrangement to be mounted to a pipeline end section in order to support a pipeline hub of the pipeline end section during and after a subsea connection of the pipeline hub to a corresponding spool piece hub that is fixed to a spool piece termination structure. The embodiments also relate to a method for mounting a connection porch of such a pipeline termination arrangement to a pipeline hub of a pipeline end section.
At an offshore well for oil and gas exploitation, a so-called spool piece may be used for connecting a termination of a longer pipeline installed on the seabed to a pipe termination of a subsea installation, such as e.g. a subsea production manifold. The spool piece is designed to span between the end points of the pipeline termination and the pipe termination in order to complete a connection between the pipeline and the pipe. The spool piece is provided with a spool piece hub which shall mate with a corresponding pipeline hub provided on the pipeline end section that is fixed to the pipeline termination.
A pipeline termination that is pre-mounted to a pipeline end section in order to support a pipeline hub of the pipeline end section during and after the connection of the pipeline hub to a corresponding spool piece hub is previously known from U.S. Pat. No. 6,142,708 A. This known pipeline termination comprises a connection porch and a landing platform. When laying a pipeline which has an end section provided with a pre-mounted pipeline termination, the size of the pipeline termination has to be adapted to the maximum available let-through opening of the tensioners on the pipe-laying vessel or the tensioners have to be adapted to the size of the pipeline termination, in order to allow the pipeline termination to pass the tensioners. The pre-mounted pipeline termination disclosed in U.S. Pat. No. 6,142,708 A is rather bulky and it is therefore not possible to lay out a pipeline provided with such a pipeline termination by means of a conventional pipe-laying vessel with capabilities related to the pipeline size rather than to a bulky pipeline termination.
Another type of pipeline termination in the form of a pipeline termination skid is previously known from WO 2006/005994 A1. This known pipeline termination skid is so designed that a pipeline end section may be mounted thereto subsea by lowering the pipeline end section into a seat of one or more holding units of the pipeline termination skid and thereafter displacing the pipeline termination skid along the pipeline end section so that the respective seat is brought into engagement with an alignment element secured about the pipeline end section so as to thereby fix the pipeline end section axially and radially in relation to the pipeline termination skid. When the pipeline end section has been secured to the pipeline termination skid, a spool piece termination structure carrying the spool piece hub and a clamping device is connectable to the pipeline termination skid by being lowered into engagement therewith. After the landing of the spool piece termination structure on the pipeline termination skid, the actual connection of the pipeline hub to the spool piece hub may be performed by displacing the clamping device and the spool piece hub in relation to the pipeline termination skid and the pipeline hub so as to bring the pipeline hub and the spool piece hub into contact with each other, whereupon the clamping device is activated so as to clamp together the pipeline hub and the spool piece hub. With the solution disclosed in WO 2006/005994 A1, no pipeline termination with a connection porch and a landing platform has to be secured to the pipeline end section before the pipeline end section is lowered into the sea from the pipe-laying vessel, which will allow the pipeline to be laid out by means of a conventional pipe-laying vessel with capabilities related to the pipeline size rather than to a bulky pipeline termination. Thus, this solution will reduce the demands on the pipe-laying vessel with respect to its equipment as compared to the prior art solution disclosed in U.S. Pat. No. 6,142,708 A. However, a disadvantage with the solution disclosed in WO 2006/005994 A1 is that subsea operations have to be carried out in order to mount the pipeline end section to the pipeline termination skid.